Fluid pumps having pumping elements that include a plunger reciprocating within a bore formed in a barrel are known. The plunger's reciprocating motion is typically accomplished with a mechanism that moves the plunger with a rotating cam. Alternatively, the plunger may contact an outer portion of a rotating angled disk or swash-plate to provide a controlled variable displacement.
A fluid pump might include a plurality of plungers that pressurize a flow of fluid, typically oil or fuel, for use in an internal combustion engine. For example, a fuel injector might use the flow of pressurized fluid, from the pump to inject the fuel or to intensify the pressure of the fuel that is injected into the engine.
Modern fuel systems use progressively higher injection pressures for injecting fuel within the engine increase the efficiency of the engine and, potentially, reduce emissions. Nevertheless, issues are presented when attempting to increase the service pressure of a fluid pump. For example, increased service pressure increases the thermal load imparted to the plunger, bore surfaces, and other pump elements. In the past, various material and design limitations have generally limited pump outlet pressures because of such thermal effects experienced by various pumping elements. To address such issues, some pump designs have incorporated larger clearances between the plunger and the barrel of pump, but such clearances can reduce the pumping efficiency of the pump, increase leakage, and potentially increase the temperature of the compressed fuel exiting the pump.